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https://github.com/mruby/mruby
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fp_uscale.c: replace fmt_fp.c and readfloat.c with uscale algorithm
Replace separate float formatting (fmt_fp.c) and parsing (readfloat.c) implementations with a unified fp_uscale.c using 128-bit unrounded scaling. Both mrb_format_float() and mrb_read_float() now share a single pow10 table and uscale() primitive for decimal/binary conversion. This fixes subnormal parsing accuracy (old code returned 0.0 for the smallest subnormals) and corrects %.2f rounding for values like 12345.125. Table size grows from ~5KB to ~11KB in .rodata. Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
@@ -41,7 +41,7 @@ module MRuby
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allocf.c
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readnum.c
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readint.c
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readfloat.c
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fp_uscale.c
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state.c
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symbol.c
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class.c
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@@ -66,7 +66,6 @@ module MRuby
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cdump.c
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codedump.c
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print.c
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fmt_fp.c
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debug.c
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etc.c
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version.c
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-380
@@ -1,380 +0,0 @@
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#include <mruby.h>
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#include <string.h>
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#ifndef MRB_NO_FLOAT
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/***********************************************************************
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Routine for converting a single-precision
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floating-point number into a string.
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The code in this function was inspired from Fred Bayer's pdouble.c.
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Since pdouble.c was released as Public Domain, I'm releasing this
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code as public domain as well.
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Dave Hylands
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The original code can be found in https://github.com/dhylands/format-float
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***********************************************************************/
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/***********************************************************************
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I modified the routine for mruby:
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* support `double`
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* support `#` (alt_form) modifier
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My modifications in this file are also placed in the public domain.
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Matz (Yukihiro Matsumoto)
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***********************************************************************/
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#include <math.h>
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#ifdef MRB_USE_FLOAT32
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// 1 sign bit, 8 exponent bits, and 23 mantissa bits.
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// exponent values 0 and 255 are reserved, exponent can be 1 to 254.
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// exponent is stored with a bias of 127.
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// The min and max floats are on the order of 1x10^37 and 1x10^-37
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#define FLT_DECEXP 32
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#define FLT_ROUND_TO_ONE 0.9999995F
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#define FLT_MIN_BUF_SIZE 6 // -9e+99
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#else
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// 1 sign bit, 11 exponent bits, and 52 mantissa bits.
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#define FLT_DECEXP 256
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#define FLT_ROUND_TO_ONE 0.999999999995
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#define FLT_MIN_BUF_SIZE 7 // -9e+199
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#endif /* MRB_USE_FLOAT32 */
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static const mrb_float g_pos_pow[] = {
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#ifndef MRB_USE_FLOAT32
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1e256, 1e128, 1e64,
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#endif
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1e32, 1e16, 1e8, 1e4, 1e2, 1e1
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};
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static const mrb_float g_neg_pow[] = {
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#ifndef MRB_USE_FLOAT32
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1e-256, 1e-128, 1e-64,
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#endif
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1e-32, 1e-16, 1e-8, 1e-4, 1e-2, 1e-1
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};
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/*
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* mrb_format_float(mrb_float f, char *buf, size_t buf_size, char fmt, int prec, char sign)
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*
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* fmt: should be one of 'e', 'E', 'f', 'F', 'g', or 'G'. (|0x80 for '#')
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* prec: is the precision (as specified in printf)
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* sign: should be '\0', '+', or ' ' ('\0' is the normal one - only print
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* a sign if ```f``` is negative. Anything else is printed as the
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* sign character for positive numbers.
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*/
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int
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mrb_format_float(mrb_float f, char *buf, size_t buf_size, char fmt, int prec, char sign) {
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char *s = buf;
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int buf_remaining = (int)buf_size - 1;
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int alt_form = 0;
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if ((uint8_t)fmt & 0x80) {
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fmt &= 0x7f; /* turn off alt_form flag */
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alt_form = 1;
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}
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if (buf_size <= FLT_MIN_BUF_SIZE) {
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// Smallest exp notion is -9e+99 (-9e+199) which is 6 (7) chars plus terminating
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// null.
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if (buf_size >= 2) {
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*s++ = '?';
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}
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if (buf_size >= 1) {
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*s++ = '\0';
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}
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return buf_size >= 2;
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}
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if (signbit(f)) {
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*s++ = '-';
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f = -f;
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}
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else if (sign) {
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*s++ = sign;
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}
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buf_remaining -= (int)(s - buf); // Adjust for sign
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{
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char uc = fmt & 0x20;
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if (isinf(f)) {
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*s++ = 'I' ^ uc;
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*s++ = 'N' ^ uc;
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*s++ = 'F' ^ uc;
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goto ret;
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}
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else if (isnan(f)) {
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*s++ = 'N' ^ uc;
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*s++ = 'A' ^ uc;
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*s++ = 'N' ^ uc;
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ret:
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*s = '\0';
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return (int)(s - buf);
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}
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}
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if (prec < 0) {
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prec = 6;
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}
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char e_char = 'E' | (fmt & 0x20); // e_char will match case of fmt
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fmt |= 0x20; // Force fmt to be lowercase
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char org_fmt = fmt;
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if (fmt == 'g' && prec == 0) {
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prec = 1;
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}
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int e, e1;
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int dec = 0;
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char e_sign = '\0';
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int num_digits = 0;
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const mrb_float *pos_pow = g_pos_pow;
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const mrb_float *neg_pow = g_neg_pow;
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if (f == 0.0) {
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e = 0;
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if (fmt == 'e') {
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e_sign = '+';
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}
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else if (fmt == 'f') {
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num_digits = prec + 1;
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}
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}
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else if (f < 1.0) { // f < 1.0
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char first_dig = '0';
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if (f >= FLT_ROUND_TO_ONE) {
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first_dig = '1';
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}
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// Build negative exponent
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for (e = 0, e1 = FLT_DECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
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if (*neg_pow > f) {
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e += e1;
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f *= *pos_pow;
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}
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}
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char e_sign_char = '-';
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if (f < 1.0) {
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if (f >= FLT_ROUND_TO_ONE) {
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f = 1.0;
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if (e == 0) {
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e_sign_char = '+';
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}
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}
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else {
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e++;
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f *= 10.0;
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}
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}
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// If the user specified 'g' format, and e is <= 4, then we'll switch
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// to the fixed format ('f')
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if (fmt == 'f' || (fmt == 'g' && e <= 4)) {
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fmt = 'f';
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dec = -1;
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*s++ = first_dig;
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if (org_fmt == 'g') {
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prec += (e - 1);
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}
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// truncate precision to prevent buffer overflow
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if (prec + 2 > buf_remaining) {
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prec = buf_remaining - 2;
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}
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num_digits = prec;
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if (num_digits || alt_form) {
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*s++ = '.';
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while (--e && num_digits) {
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*s++ = '0';
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num_digits--;
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}
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}
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}
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else {
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// For e & g formats, we'll be printing the exponent, so set the
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// sign.
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e_sign = e_sign_char;
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dec = 0;
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if (prec > (buf_remaining - FLT_MIN_BUF_SIZE)) {
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prec = buf_remaining - FLT_MIN_BUF_SIZE;
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if (fmt == 'g') {
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prec++;
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}
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}
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}
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}
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else {
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// Build positive exponent
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for (e = 0, e1 = FLT_DECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
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if (*pos_pow <= f) {
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e += e1;
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f *= *neg_pow;
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}
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}
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// correct for FP rounding errors in the power-of-10 loop
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// (e.g. x87 extended precision can leave f >= 10.0)
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if (f >= 10.0) {
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f *= 0.1;
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e++;
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}
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// If the user specified fixed format (fmt == 'f') and e makes the
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// number too big to fit into the available buffer, then we'll
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// switch to the 'e' format.
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if (fmt == 'f') {
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if (e >= buf_remaining) {
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fmt = 'e';
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}
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else if ((e + prec + 2) > buf_remaining) {
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prec = buf_remaining - e - 2;
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if (prec < 0) {
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// This means no decimal point, so we can add one back
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// for the decimal.
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prec++;
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}
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}
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}
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if (fmt == 'e' && prec > (buf_remaining - 6)) {
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prec = buf_remaining - 6;
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}
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// If the user specified 'g' format, and e is < prec, then we'll switch
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// to the fixed format.
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if (fmt == 'g' && e < prec) {
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fmt = 'f';
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prec -= (e + 1);
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}
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if (fmt == 'f') {
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dec = e;
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num_digits = prec + e + 1;
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}
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else {
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e_sign = '+';
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}
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}
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if (prec < 0) {
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// This can happen when the prec is trimmed to prevent buffer overflow
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prec = 0;
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}
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// We now have f as a floating-point number between >= 1 and < 10
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// (or equal to zero), and e contains the absolute value of the power of
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// 10 exponent, and (dec + 1) == the number of digits before the decimal.
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// For e, prec is # digits after the decimal
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// For f, prec is # digits after the decimal
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// For g, prec is the max number of significant digits
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//
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// For e & g there will be a single digit before the decimal
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// for f there will be e digits before the decimal
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if (fmt == 'e') {
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num_digits = prec + 1;
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if (prec == 0) prec = 1;
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}
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else if (fmt == 'g') {
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num_digits = prec;
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}
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// Print the digits of the mantissa
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for (int i = 0; i < num_digits; i++,dec--) {
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int8_t d = (int8_t)f;
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if (d > 9) d = 9;
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if (d < 0) d = 0;
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*s++ = '0' + d;
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if (dec == 0 && (prec > 0 || alt_form)) {
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*s++ = '.';
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}
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f -= (mrb_float)d;
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f *= 10.0;
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}
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// Round
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if (f >= 5.0) {
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char *rs = s;
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rs--;
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while (1) {
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if (*rs == '.') {
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rs--;
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continue;
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}
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if (*rs < '0' || *rs > '9') {
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// + or -
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rs++; // So we sit on the digit to the right of the sign
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break;
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}
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if (*rs < '9') {
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(*rs)++;
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break;
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}
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*rs = '0';
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if (rs == buf) {
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break;
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}
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rs--;
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}
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if (*rs == '0') {
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// We need to insert a 1
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if (fmt != 'f' && rs[1] == '.') {
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// We're going to round 9.99 to 10.00
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// Move the decimal point
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rs[0] = '.';
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rs[1] = '0';
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if (e_sign == '-') {
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e--;
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}
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else {
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e++;
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}
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}
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s++;
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char *ss = s;
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while (ss > rs) {
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*ss = ss[-1];
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ss--;
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}
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*rs = '1';
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if (f < 1.0 && fmt == 'f') {
|
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// We rounded up to 1.0
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prec--;
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}
|
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}
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}
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|
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if (org_fmt == 'g' && prec > 0 && !alt_form) {
|
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// Remove trailing zeros and a trailing decimal point
|
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while (s[-1] == '0') {
|
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s--;
|
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}
|
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if (s[-1] == '.') {
|
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s--;
|
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}
|
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}
|
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// Append the exponent
|
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if (e_sign) {
|
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*s++ = e_char;
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*s++ = e_sign;
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if (e >= 100) {
|
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*s++ = '0' + (e / 100);
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e %= 100;
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}
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*s++ = '0' + (e / 10);
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*s++ = '0' + (e % 10);
|
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}
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|
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*s = '\0';
|
||||
return (int)(s - buf);
|
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}
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#endif
|
||||
+1359
File diff suppressed because it is too large
Load Diff
-229
@@ -1,229 +0,0 @@
|
||||
#include <mruby.h>
|
||||
|
||||
#ifndef MRB_NO_FLOAT
|
||||
|
||||
#include <string.h>
|
||||
#include <math.h>
|
||||
#include <stdint.h>
|
||||
|
||||
// Powers of 10 lookup table for better performance and accuracy
|
||||
static const double pow10_positive[] = {
|
||||
1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
|
||||
1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
|
||||
1e20, 1e21, 1e22, 1e23, 1e24, 1e25, 1e26, 1e27, 1e28, 1e29,
|
||||
1e30, 1e31, 1e32, 1e33, 1e34, 1e35, 1e36, 1e37, 1e38, 1e39,
|
||||
1e40, 1e41, 1e42, 1e43, 1e44, 1e45, 1e46, 1e47, 1e48, 1e49,
|
||||
1e50, 1e51, 1e52, 1e53, 1e54, 1e55, 1e56, 1e57, 1e58, 1e59,
|
||||
1e60, 1e61, 1e62, 1e63, 1e64, 1e65, 1e66, 1e67, 1e68, 1e69,
|
||||
1e70, 1e71, 1e72, 1e73, 1e74, 1e75, 1e76, 1e77, 1e78, 1e79,
|
||||
1e80, 1e81, 1e82, 1e83, 1e84, 1e85, 1e86, 1e87, 1e88, 1e89,
|
||||
1e90, 1e91, 1e92, 1e93, 1e94, 1e95, 1e96, 1e97, 1e98, 1e99,
|
||||
1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109,
|
||||
1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119,
|
||||
1e120, 1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129,
|
||||
1e130, 1e131, 1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139,
|
||||
1e140, 1e141, 1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149,
|
||||
1e150, 1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159,
|
||||
1e160, 1e161, 1e162, 1e163, 1e164, 1e165, 1e166, 1e167, 1e168, 1e169,
|
||||
1e170, 1e171, 1e172, 1e173, 1e174, 1e175, 1e176, 1e177, 1e178, 1e179,
|
||||
1e180, 1e181, 1e182, 1e183, 1e184, 1e185, 1e186, 1e187, 1e188, 1e189,
|
||||
1e190, 1e191, 1e192, 1e193, 1e194, 1e195, 1e196, 1e197, 1e198, 1e199,
|
||||
1e200, 1e201, 1e202, 1e203, 1e204, 1e205, 1e206, 1e207, 1e208, 1e209,
|
||||
1e210, 1e211, 1e212, 1e213, 1e214, 1e215, 1e216, 1e217, 1e218, 1e219,
|
||||
1e220, 1e221, 1e222, 1e223, 1e224, 1e225, 1e226, 1e227, 1e228, 1e229,
|
||||
1e230, 1e231, 1e232, 1e233, 1e234, 1e235, 1e236, 1e237, 1e238, 1e239,
|
||||
1e240, 1e241, 1e242, 1e243, 1e244, 1e245, 1e246, 1e247, 1e248, 1e249,
|
||||
1e250, 1e251, 1e252, 1e253, 1e254, 1e255, 1e256, 1e257, 1e258, 1e259,
|
||||
1e260, 1e261, 1e262, 1e263, 1e264, 1e265, 1e266, 1e267, 1e268, 1e269,
|
||||
1e270, 1e271, 1e272, 1e273, 1e274, 1e275, 1e276, 1e277, 1e278, 1e279,
|
||||
1e280, 1e281, 1e282, 1e283, 1e284, 1e285, 1e286, 1e287, 1e288, 1e289,
|
||||
1e290, 1e291, 1e292, 1e293, 1e294, 1e295, 1e296, 1e297, 1e298, 1e299,
|
||||
1e300, 1e301, 1e302, 1e303, 1e304, 1e305, 1e306, 1e307, 1e308
|
||||
};
|
||||
|
||||
static const double pow10_negative[] = {
|
||||
1e0, 1e-1, 1e-2, 1e-3, 1e-4, 1e-5, 1e-6, 1e-7, 1e-8, 1e-9,
|
||||
1e-10, 1e-11, 1e-12, 1e-13, 1e-14, 1e-15, 1e-16, 1e-17, 1e-18, 1e-19,
|
||||
1e-20, 1e-21, 1e-22, 1e-23, 1e-24, 1e-25, 1e-26, 1e-27, 1e-28, 1e-29,
|
||||
1e-30, 1e-31, 1e-32, 1e-33, 1e-34, 1e-35, 1e-36, 1e-37, 1e-38, 1e-39,
|
||||
1e-40, 1e-41, 1e-42, 1e-43, 1e-44, 1e-45, 1e-46, 1e-47, 1e-48, 1e-49,
|
||||
1e-50, 1e-51, 1e-52, 1e-53, 1e-54, 1e-55, 1e-56, 1e-57, 1e-58, 1e-59,
|
||||
1e-60, 1e-61, 1e-62, 1e-63, 1e-64, 1e-65, 1e-66, 1e-67, 1e-68, 1e-69,
|
||||
1e-70, 1e-71, 1e-72, 1e-73, 1e-74, 1e-75, 1e-76, 1e-77, 1e-78, 1e-79,
|
||||
1e-80, 1e-81, 1e-82, 1e-83, 1e-84, 1e-85, 1e-86, 1e-87, 1e-88, 1e-89,
|
||||
1e-90, 1e-91, 1e-92, 1e-93, 1e-94, 1e-95, 1e-96, 1e-97, 1e-98, 1e-99,
|
||||
1e-100, 1e-101, 1e-102, 1e-103, 1e-104, 1e-105, 1e-106, 1e-107, 1e-108, 1e-109,
|
||||
1e-110, 1e-111, 1e-112, 1e-113, 1e-114, 1e-115, 1e-116, 1e-117, 1e-118, 1e-119,
|
||||
1e-120, 1e-121, 1e-122, 1e-123, 1e-124, 1e-125, 1e-126, 1e-127, 1e-128, 1e-129,
|
||||
1e-130, 1e-131, 1e-132, 1e-133, 1e-134, 1e-135, 1e-136, 1e-137, 1e-138, 1e-139,
|
||||
1e-140, 1e-141, 1e-142, 1e-143, 1e-144, 1e-145, 1e-146, 1e-147, 1e-148, 1e-149,
|
||||
1e-150, 1e-151, 1e-152, 1e-153, 1e-154, 1e-155, 1e-156, 1e-157, 1e-158, 1e-159,
|
||||
1e-160, 1e-161, 1e-162, 1e-163, 1e-164, 1e-165, 1e-166, 1e-167, 1e-168, 1e-169,
|
||||
1e-170, 1e-171, 1e-172, 1e-173, 1e-174, 1e-175, 1e-176, 1e-177, 1e-178, 1e-179,
|
||||
1e-180, 1e-181, 1e-182, 1e-183, 1e-184, 1e-185, 1e-186, 1e-187, 1e-188, 1e-189,
|
||||
1e-190, 1e-191, 1e-192, 1e-193, 1e-194, 1e-195, 1e-196, 1e-197, 1e-198, 1e-199,
|
||||
1e-200, 1e-201, 1e-202, 1e-203, 1e-204, 1e-205, 1e-206, 1e-207, 1e-208, 1e-209,
|
||||
1e-210, 1e-211, 1e-212, 1e-213, 1e-214, 1e-215, 1e-216, 1e-217, 1e-218, 1e-219,
|
||||
1e-220, 1e-221, 1e-222, 1e-223, 1e-224, 1e-225, 1e-226, 1e-227, 1e-228, 1e-229,
|
||||
1e-230, 1e-231, 1e-232, 1e-233, 1e-234, 1e-235, 1e-236, 1e-237, 1e-238, 1e-239,
|
||||
1e-240, 1e-241, 1e-242, 1e-243, 1e-244, 1e-245, 1e-246, 1e-247, 1e-248, 1e-249,
|
||||
1e-250, 1e-251, 1e-252, 1e-253, 1e-254, 1e-255, 1e-256, 1e-257, 1e-258, 1e-259,
|
||||
1e-260, 1e-261, 1e-262, 1e-263, 1e-264, 1e-265, 1e-266, 1e-267, 1e-268, 1e-269,
|
||||
1e-270, 1e-271, 1e-272, 1e-273, 1e-274, 1e-275, 1e-276, 1e-277, 1e-278, 1e-279,
|
||||
1e-280, 1e-281, 1e-282, 1e-283, 1e-284, 1e-285, 1e-286, 1e-287, 1e-288, 1e-289,
|
||||
1e-290, 1e-291, 1e-292, 1e-293, 1e-294, 1e-295, 1e-296, 1e-297, 1e-298, 1e-299,
|
||||
1e-300, 1e-301, 1e-302, 1e-303, 1e-304, 1e-305, 1e-306, 1e-307, 1e-308, 1e-309,
|
||||
1e-310, 1e-311, 1e-312, 1e-313, 1e-314, 1e-315, 1e-316, 1e-317, 1e-318, 1e-319,
|
||||
1e-320, 1e-321, 1e-322, 1e-323
|
||||
};
|
||||
|
||||
#define POW10_POSITIVE_SIZE (sizeof(pow10_positive) / sizeof(pow10_positive[0]))
|
||||
#define POW10_NEGATIVE_SIZE (sizeof(pow10_negative) / sizeof(pow10_negative[0]))
|
||||
|
||||
static double
|
||||
mrb_pow10(int exp)
|
||||
{
|
||||
if (exp >= 0) {
|
||||
if (exp < (int)POW10_POSITIVE_SIZE) {
|
||||
return pow10_positive[exp];
|
||||
}
|
||||
return HUGE_VAL;
|
||||
}
|
||||
else {
|
||||
exp = -exp;
|
||||
if (exp < (int)POW10_NEGATIVE_SIZE) {
|
||||
return pow10_negative[exp];
|
||||
}
|
||||
return 0.0;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
** Parses a string representation of a floating-point number.
|
||||
**
|
||||
** @param str The input string to parse.
|
||||
** @param endp A pointer to a char* that will be updated to point to the
|
||||
** character in str after the last character used in the
|
||||
** conversion. Can be NULL.
|
||||
** @param fp A pointer to a double that will be set to the parsed
|
||||
** floating-point number.
|
||||
** @return TRUE if a float is successfully parsed, FALSE otherwise.
|
||||
*/
|
||||
MRB_API mrb_bool
|
||||
mrb_read_float(const char *str, char **endp, double *fp)
|
||||
{
|
||||
const char *p = str;
|
||||
const char *a = p;
|
||||
uint64_t int_part = 0;
|
||||
uint64_t frac_part = 0;
|
||||
int frac_digits = 0;
|
||||
int sign = 1;
|
||||
int digits = 0;
|
||||
int overflow = 0;
|
||||
|
||||
// Skip whitespace
|
||||
while (ISSPACE((unsigned char)*p)) p++;
|
||||
|
||||
// Handle sign
|
||||
if (*p == '-') { sign = -1; p++; }
|
||||
else if (*p == '+') p++;
|
||||
|
||||
// Parse integer part using integer arithmetic for better accuracy
|
||||
while (ISDIGIT(*p)) {
|
||||
if (int_part > (UINT64_MAX - 9) / 10) {
|
||||
overflow = 1;
|
||||
// Continue parsing to find the end
|
||||
while (ISDIGIT(*p)) p++;
|
||||
break;
|
||||
}
|
||||
int_part = int_part * 10 + (*p - '0');
|
||||
digits++;
|
||||
a = ++p;
|
||||
}
|
||||
|
||||
// Parse fractional part
|
||||
if (*p == '.') {
|
||||
p++;
|
||||
while (ISDIGIT(*p) && frac_digits < 18) { // Limit precision to avoid overflow
|
||||
frac_part = frac_part * 10 + (*p - '0');
|
||||
frac_digits++;
|
||||
digits++;
|
||||
p++;
|
||||
}
|
||||
// Skip remaining fractional digits if any
|
||||
while (ISDIGIT(*p)) p++;
|
||||
a = p;
|
||||
}
|
||||
|
||||
// If no digits were found, return FALSE
|
||||
if (digits == 0) {
|
||||
if (endp) *endp = (char*)str;
|
||||
*fp = 0.0;
|
||||
return FALSE;
|
||||
}
|
||||
|
||||
double res;
|
||||
if (overflow) {
|
||||
// For overflow case, fall back to floating point parsing
|
||||
res = (double)int_part;
|
||||
}
|
||||
else {
|
||||
// Divide by the exact 10^n (exact for n <= 22) rather than multiplying
|
||||
// by the inexact 10^-n, so the fraction is correctly rounded.
|
||||
res = (double)int_part;
|
||||
if (frac_digits > 0) {
|
||||
res += (double)frac_part / mrb_pow10(frac_digits);
|
||||
}
|
||||
}
|
||||
|
||||
// Handle exponent
|
||||
if ((*p | 32) == 'e') {
|
||||
int e = 0;
|
||||
int exp_sign = 1;
|
||||
p++;
|
||||
if (*p == '-') { exp_sign = -1; p++; }
|
||||
else if (*p == '+') p++;
|
||||
|
||||
// If no digits follow 'e', ignore the exponent part
|
||||
if (!ISDIGIT(*p)) goto done;
|
||||
|
||||
while (ISDIGIT(*p)) {
|
||||
if (e < 10000) { // Prevent integer overflow
|
||||
e = e * 10 + (*p - '0');
|
||||
}
|
||||
p++;
|
||||
}
|
||||
e *= exp_sign;
|
||||
|
||||
// Apply exponent directly - let mrb_pow10 handle overflow
|
||||
// Large exponents will return HUGE_VAL (infinity) or 0.0 as appropriate
|
||||
|
||||
res *= mrb_pow10(e);
|
||||
a = p;
|
||||
}
|
||||
|
||||
// Apply sign
|
||||
res *= sign;
|
||||
|
||||
// Set endp
|
||||
done:
|
||||
if (endp) *endp = (char*)a;
|
||||
*fp = res;
|
||||
|
||||
// strtod(3) stores ERANGE to errno for overflow/underflow
|
||||
// mruby does not require those checks
|
||||
#if 0
|
||||
// Check for underflow after applying the exponent
|
||||
if (res != 0.0 && fabs(res) < DBL_MIN) {
|
||||
return FALSE;
|
||||
}
|
||||
|
||||
// Check if the result is infinity or NaN
|
||||
if (isinf(res) || isnan(res)) {
|
||||
return FALSE;
|
||||
}
|
||||
#endif
|
||||
return TRUE;
|
||||
}
|
||||
|
||||
#endif
|
||||
Executable
+68
@@ -0,0 +1,68 @@
|
||||
#!/usr/bin/env ruby
|
||||
# frozen_string_literal: true
|
||||
|
||||
# Generate pow10 table for mruby unrounded scaling (fp_uscale.c)
|
||||
#
|
||||
# Uses exact integer arithmetic only.
|
||||
# For each p in [-343, 341], computes (hi, lo) such that:
|
||||
# 10^p ~= (hi * 2^64 - lo) * 2^pe
|
||||
# where pe = floor(p * log2(10)) - 127
|
||||
#
|
||||
# The 128-bit value pm = hi * 2^64 - lo is in [2^127, 2^128).
|
||||
|
||||
POW10_MIN = -343
|
||||
POW10_MAX = 341
|
||||
|
||||
def generate_entry(p)
|
||||
if p >= 0
|
||||
val = 10**p
|
||||
bit_len = val.bit_length
|
||||
pe = bit_len - 128
|
||||
if pe >= 0
|
||||
mask = (1 << pe) - 1
|
||||
pm = (val >> pe) + ((val & mask) != 0 ? 1 : 0)
|
||||
else
|
||||
pm = val << (-pe)
|
||||
end
|
||||
else
|
||||
abs_p = -p
|
||||
denom = 10**abs_p
|
||||
# pe = floor(p * log2(10)) - 127
|
||||
# Ruby's integer division of negative numbers does floor division
|
||||
pe_est = (p * 108853 >> 15) - 127
|
||||
|
||||
numerator = 1 << (-pe_est)
|
||||
pm = (numerator + denom - 1) / denom
|
||||
|
||||
# Adjust pe if pm is out of range [2^127, 2^128)
|
||||
while pm >= (1 << 128)
|
||||
pe_est += 1
|
||||
numerator = 1 << (-pe_est)
|
||||
pm = (numerator + denom - 1) / denom
|
||||
end
|
||||
while pm < (1 << 127)
|
||||
pe_est -= 1
|
||||
numerator = 1 << (-pe_est)
|
||||
pm = (numerator + denom - 1) / denom
|
||||
end
|
||||
end
|
||||
|
||||
raise "pm out of range for p=#{p}: #{pm.bit_length}" unless pm.bit_length == 128
|
||||
|
||||
hi = (pm >> 64) + ((pm & ((1 << 64) - 1)) != 0 ? 1 : 0)
|
||||
lo = (hi << 64) - pm
|
||||
|
||||
raise "hi out of range for p=#{p}" unless hi >= (1 << 63) && hi < (1 << 64)
|
||||
|
||||
{ hi: hi, lo: lo }
|
||||
end
|
||||
|
||||
def main
|
||||
entries = (POW10_MIN..POW10_MAX).map { |p| [p, generate_entry(p)] }
|
||||
|
||||
entries.each do |p, e|
|
||||
printf(" {0x%016xULL, 0x%016xULL},\n", e[:hi], e[:lo])
|
||||
end
|
||||
end
|
||||
|
||||
main
|
||||
Reference in New Issue
Block a user